Manufacturers of corrugated paper products, known as Box Makers, produce both foldable boxes which have been folded and glued at the factory and die cut flat sheets which may be used either in their flat state or folded into a desired shape. These will be referred to as folded boxes and flat boxes respectively. The term boxes alone can refer to both folded and flat boxes.
Both the folded boxes and the flat boxes are produced by Converting machinery which processes the Corrugated Sheet Stock produced by the machinery known as a Corrugator. The Corrugated Sheet Stock is corrugated material cut to a specific size with optional scoring. Scoring is the intentional crushing of the corrugated flutes in order to allow folding of the corrugated material. However, the corrugated sheet stock has not been cut or notched to the detail typically required to produce the final foldable boxes or the flat boxes.
Often customized printing is required on boxes which may be done by 1) using a preprinted material integrated into the corrugated sheet stock on the Corrugator, 2) using flexographic printing during the Converting process or 3) applying ink or labels post Converting through various techniques.
During the Converting process the Corrugated Sheet Stock is transformed into a box by performing additional cutting and optionally adding scoring and printing. There are multiple possible purposes for the additional cutting of the Corrugated Sheet Stock. Many of these cutting operations will result in pieces of the original Corrugated Sheet Stock being completely separated from the final box. These pieces are in general referred to as Scrap.
As the boxes are produced there are a variety of methods to form Stacks of the boxes which in turn are sold to other companies which will be referred to as the Box Customer. There are a multitude of applications for these boxes and there are many reasons why it is undesirable for the Scrap to be included in shipment to the Box Customer. Erecting of the box is the process of taking the box and manipulating it by folding, bending, interlocking, stapling, taping, etc. in order for the box to be ready for its final usage. For Box Customers that manually erect their Boxes, the inclusion of Scrap is undesirable because of the additional mess created. For Box Customers that use automatic machinery to erect their Boxes, the Scrap can lead to jams in their machinery causing undesirable downtime and lower production. For Box Customers that use the box for food, such as a pizza box, having Scrap included in the final erected box is clearly undesirable.
The operators that work for the Box Maker are required to keep up a certain level of cleanliness which is often referred to as house cleaning. The Box Maker prefers that the amount of time required for house cleaning be held to a minimum between orders and certainly do not want to have to stop running a current in order to perform house cleaning.
One of the significant items to deal with is any scrap that gets pass outside the machinery and onto the floor of the box plant. This is particularly true if the scrap gets into an area which if difficult for the operator to get access.
The Box Maker typically has a multitude of machinery requiring compressed air and normally there is a central air compression system which feeds the entire box plant. There is both a cost in electrical energy and system maintenance associated with an increase in compressed air usage. Thus, any usage of compressed air, particularly on a continuous basis needs to be justified by the Box Maker.
In the conversion of the Corrugated Sheet Stock into Boxes the material is fed through machinery. The Lead Edge for both Corrugated Sheet Stock and Boxes refers to the first edge of travel across the machine whereas the Trailing Edge refers to the last edge of travel across the machine. The Corrugated Sheet Stock may be cut completely in the cross-machine direction in one or more locations to create two or more boxes in the through-machine direction. These are referred to as Ups. The Corrugated Sheet Stock may be cut completely in the through-machine direction in one or more locations to create two or more boxes in the cross-machine direction. These are referred to as Outs.
There are multiple methods by which the cutting of the Corrugated Sheet Stock may be accomplished during the Converting process. One example method for cutting Corrugated Sheet Stock is known as Rotary Die Cutting. A typical configuration of a Rotary Die Cutter, known as Rule and Rubber, uses of a pair of cylinders where the lower cylinder, known as the Anvil, is covered in a firm but soft rubber material and the top cylinder is mounted with a Die Board. The Die Board is normally a curved plywood base in which embedded are a customized set of steel Rules, which protrude from the plywood base and when rotated with the Anvil will cut and score the Corrugated Sheet Stock into the final desired box. The transportation speed of the box, as determined by the effective linear speed at the nip of the Die Board and Anvil, is known as Line Speed. Also relevant would be the similar process of steel-on-on steel Rotary Die Cutting. The Rotary Die Cutting process is relevant since there is not an integral method in the process for positive separation of the Scrap from the box.
In the normal production process, when changing the order to a different box, the Die Boards and Ink Plates must be changed on the Rotary Die Cutter. The Ink Plate Access is typically provided by the design of the Rotary Die Cutter. One of the common methods for allowing the operator to change the Die Boards, known as Die Board Access, is to have the stacking apparatus downstream of the Rotary Die Cutter move out of the way enough for one or more people to be able to walk into the area and swap out the Die Boards.
The Box Makers typically have many customers and a wide variety of different style of boxes which need to be produced. They need to set up and run many different orders during a given production period. The Box Maker is highly motivated to reduce the time used for setting up a new order. This is known as Order Setup Time.
An improvement in Order Setup Time can be achieved by making it more efficient to allow the operator to get access to the Sample Sheets. Sample Sheets include flat boxes that are ejected from the Converting machinery prior to being added to the stacks of finished boxes. Operators can inspect the Test Sheets to verify quality.
A Sheet Stacking Apparatus has the purpose of receiving the boxes being produced by a Rotary Die Cutter and transporting the boxes through the apparatus such that stacks of the boxes are created and exit from the discharge end of the apparatus.
The Sheet Stacking Apparatus needs to transport the boxes and does so using one or more means of conveyance. There are multiple means possible, including but not limited to conveyor belts configured above and below the boxes creating a sandwiching effect, conveyor belts below the boxes using gravity to hold down the boxes, conveyor belts below the boxes with vacuum chambers providing gravity assist, conveyor belts above the boxes with vacuum chambers using air pressure to hold up the boxes, series of wheel assemblies above and below the boxes creating a sandwiching effect, series of wheel assemblies below the boxes using gravity to hold down the boxes, and other suitable means.
The Sheet Stacking Apparatus for the Rotary Die Cutter has four functional modules.
The first functional module at the receiving end of the apparatus is typically referred to as the Layboy Function. Its function is the receiving of the boxes from the Rotary Die Cutter and assisting in the removing of the scrap from the boxes. Often speed variations are implemented in the section in preparation for the second functional module. Since the Die Drum of the Rotary Die Cutter is two cylinders and the Layboy Conveyor must have a finite thickness, designers are left with a distance between the Die Board nip and the conveying surfaces of the Layboy Function. This is the distance of no support for the boxes transitioning from the Rotary Die Cutter to the stacking apparatus and can be referred to as the RDC-Layboy Gap. It has been learned by the operators that one of the simplest ways to improve the scrap removal process is to increase the Layboy Roll Out. The Layboy Roll Out moves the conveying surfaces of the Layboy Function away from the Rotary Die Cutter thus increasing the RDC-Layboy Gap. While this increases the distance of no support for the boxes it also creates an increased opportunity for the scrap to fall away from the boxes. While on short boxes Layboy Roll Out is not practical as the lack of support leads to loss of control of the box, for longer boxes Layboy Roll Out is very effective in allowing better scrap removal without loss of box control. It is not uncommon to have Layboy Roll Out of 8 inches or greater. It is desirable for the operator to be able to increase the Layboy Roll Out during normal production operations without stopping the flow of boxes through the Sheet Stacking Apparatus. This ability is referred to as Running Layboy Roll Out.
The second functional module will be referred to as the Shingling Function. This is the widely used option in the stacking process where the boxes can be changed from Stream Mode to Shingle Mode. Stream Mode is where the boxes are being conveyed without overlap at higher speed stream. Shingle Mode happens with a transition to conveying means that are running slower than Line Speed and thus the boxes overlap and create what is known as Shingle of boxes. The speed variations referred to in the Layboy Function may to higher than Line Speed to pull gaps between the boxes to allow the creation of the Shingle of boxes.
The third functional module will be referred to as the Stacking Function. The boxes are now conveyed in either Stream Mode or Shingle Mode to where the stack of boxes is being created. The Stacking Conveyor changes elevation in order to accommodate the elevation change of the growing stack of boxes such that the conveyed boxes are deposited on the top of the stack. An alternative method is for the Stacking Conveyor to remain at a fixed elevation and the Stack Support Surface under the growing stack of boxes can move down, again such that the conveyed boxes are deposited on the top of the stack. An additional alternative is a combination of the Stacking Conveyor and the Stack Support Surface changing elevation.
The fourth functional module will be referred to as the Hopper Function. This is where the full stack of boxes or bundles of boxes are stacked and includes an Accumulation means. The accumulation means can be done by one of many well know techniques but all are common in allowing the temporary storage of boxes while the completed full stack or bundles are being conveyed out of the Hopper area. These boxes then become the base for the next full stack or bundles.
Some Stacking Apparatus require the individual boxes to be separated lateral across the machine in order to make individual stacking in the Hopper Function. This can be during the Layboy Function, the Shingling Function or the Stacking Function. If and where it is done has no relevance to the technology described herein.
The quality of the box surface and print quality is an important factor to the Box Maker. Allowing the operator to easily get a Sample Sheet is desirable. During set up of the Rotary Die Cutter there are multiple adjustments to the Rotary Die Cutter that need to checked which is ultimately checked with a visual inspection of one or more Sample Sheets after the Die Boards and Ink Plates for the new order have been changed. Often the penetration of the Die Board in intentionally reduced and a full Corrugate Sheet is fed so the Ink Plates print on the board but the die cut pattern showing the shape of the box is only imprinted. The results are the Ups and Outs are all still attached and the one large sheet can be inspected to confirm and adjust the registration of the various Ink Plates and Die Board. The operator may then fully engage the Die Board for full penetration, resulting in fully separated multiple Ups and Outs (Boxes) to be tested and inspected. The ability to provide the operator a Sample Sheet means the full imprinted Corrugated Sheet or Boxes are delivered to the operator for easy access. It does not include simply going to the discharge end in the Hopper Function or reaching into the Shingle Function or Stacking Function areas as modern machinery is required to be well guarded in these areas.
Historically, one method of providing Die Board Access was to put the entire Sheet Stacking Apparatus on wheels and roll the machinery away from the Rotary Die Cutter during order change. This also provided the operator with a means for adjusting the Layboy Roll Out. With the advent of Bundle Breaker lines, which often adds right angle take off system to the Hopper Function of the stacking apparatus having the Sheet Stacking Apparatus and its Hopper Function roll into this downstream space is less than desirable. Additionally, safety standards are now requiring hand rails on some of these downstream conveyors which are being classified as platforms. These hand rails and moving the Hopper Function can interfere or create additional hazards. Finally, while this does provide a means for the operator to adjust the Layboy Roll Out, since the Layboy Function and Hopper Function move as a unit, the operator must stop the production of boxes, make the adjustment and then re-start the production. If a partial stack has already been created, the operator must additionally adjust the partial stack by moving it under the new position of the Hopper Function and re-engage into the stack. Finally, having the entire Sheet Stacking Apparatus on wheels does not provide any means to provide the operator with Sample Sheets.
Prior Sheet Stacking Apparatus with fixed position Hopper Functions do not provide all the features of Die Board Access, Running Layboy Roll Out and Sample Sheets.